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package org.apache.juneau.transforms;

import static org.apache.juneau.internal.IOUtils.*;

import java.io.*;

import org.apache.juneau.*;
import org.apache.juneau.html.*;
import org.apache.juneau.json.*;
import org.apache.juneau.parser.*;
import org.apache.juneau.transform.*;
import org.apache.juneau.uon.*;
import org.apache.juneau.urlencoding.*;
import org.apache.juneau.xml.*;

/**
 * Transforms the contents of a {@link Reader} into an {@code Object}.
 * 
 * <h5 class='topic'>Description</h5>
 * 
 * The {@code Reader} must contain JSON, Juneau-generated XML (output from {@link XmlSerializer}), or Juneau-generated
 * HTML (output from {@link JsonSerializer}) in order to be parsed correctly.
 * 
 * <p>
 * Useful for serializing models that contain {@code Readers} created by {@code RestCall} instances.
 * 
 * <p>
 * This is a one-way transform, since {@code Readers} cannot be reconstituted.
 * 
 * <h5 class='topic'>Behavior-specific subclasses</h5>
 * 
 * The following direct subclasses are provided for convenience:
 * <ul>
 * 	<li>{@link Json} - Parses JSON text.
 * 	<li>{@link Xml} - Parses XML text.
 * 	<li>{@link Html} - Parses HTML text.
 * 	<li>{@link PlainText} - Parses plain text.
 * </ul>
 */
public class ReaderSwap extends PojoSwap<Reader,Object> {

	/** Reader transform for reading JSON text. */
	public static class Json extends ReaderSwap {
		/** Constructor */
		public Json() {
			super(JsonParser.DEFAULT);
		}
	}

	/** Reader transform for reading XML text. */
	public static class Xml extends ReaderSwap {
		/** Constructor */
		public Xml() {
			super(XmlParser.DEFAULT);
		}
	}

	/** Reader transform for reading HTML text. */
	public static class Html extends ReaderSwap {
		/** Constructor */
		public Html() {
			super(HtmlParser.DEFAULT);
		}
	}

	/** Reader transform for reading plain text. */
	public static class PlainText extends ReaderSwap {
		/** Constructor */
		public PlainText() {
			super(null);
		}
	}

	/** Reader transform for reading plain text. */
	public static class Uon extends ReaderSwap {
		/** Constructor */
		public Uon() {
			super(UonParser.DEFAULT);
		}
	}

	/** Reader transform for reading plain text. */
	public static class UrlEncoding extends ReaderSwap {
		/** Constructor */
		public UrlEncoding() {
			super(UrlEncodingParser.DEFAULT);
		}
	}
	
	/** The parser to use to parse the contents of the Reader. */
	private ReaderParser parser;

	/**
	 * @param parser The parser to use to convert the contents of the reader to Java objects.
	 */
	public ReaderSwap(ReaderParser parser) {
		this.parser = parser;
	}

	/**
	 * Converts the specified {@link Reader} to an {@link Object} whose type is determined by the contents of the reader.
	 */
	@Override /* PojoSwap */
	public Object swap(BeanSession session, Reader o) throws Exception {
		if (parser == null)
			return read(o);
		return parser.parse(o, Object.class);
	}
}
